Now I am on the verge of of physics board exam but totally got hanged with all these physics relations and formulas.
Hello! Well first of all physics is not just about knowing relations and formulas. Before getting into the matehmatic apparatus of this science you need to be sure that you understand completely the phenonemon about you study. The laws of physics, which are those 'forumlas' you refferd to are first observed as a phenomenon, and then the scientist get into doing math, that means finding quantitative relations that can describe the phenomenon. For example, before Newton discovered gravitation, he had observed that every object thrown tends to fall back on the surface of the earth.
Secondly, there are two types of relations: the basic laws, and relations derived with these laws as a base. For example, if you know Snell's law (the basic law), then you can derive the equations of the diopter. Snell's law has been discovered experimentally. But to find the equations of the diopter (or lens) you need to do some math, in this case some basic Eucledian geometry. What you need to rembember is only the basic laws! Why? Well, simply because it would take too much work to redesign the experiments that led to their discovery. The other relations, you derive them when you need them. For solving problems it's good to also memorize the derived relations, but you need to make sure that you can derive them again in case you forget them.
How can I remember all these derivations of formulas, one which I wonder why these stuffs is useful in our life?
This 'stuff' is actually very useful. Physics is everywhere! Think about the glasses we wear to correct the defects of our eyes, or about the simple act of walking, and you'll se why it's so useful.
Please can aybody help me to gain a good marks in physics...
If you have any questions about a certain subject post it on this forum! There are plenty of people who can help you. We can't do anything more.
I wish you good luck with your exams!